The present invention relates to a new and improved means for measuring the muzzle velocity of a projectile launched from a weapon. In prior art, muzzle velocity has been measured in many different ways. Such ways have included breaking spaced wires, passing through two or more narrow light screens, measuring the Doppler shift of light/IR/radar signals reflected down a barrel, using dual magnetic or Hall-effect sensors to pick up the projectile body, and using optical sensors to detect light/dark stripes on the projectile wall.
The problem with all of the prior techniques for measuring muzzle velocity is that none can provide .+-.0.1% accuracy while at the same time capable of being included in an easily portable muzzle attachment. For example, light-screens and Doppler techniques can give the desired accuracy, but both require a pre-configured test range. On the other hand, optical sensors can be included in an easily portable muzzle attachment, but they are unreliable due to gas and flame blow-by obscuring the optical image. Furthermore, residue deposited on the optical sensor window when the projectile is fired obscures the image.
Sensing of projectile stripes is less sensitive to blow-by or soot, but it requires specially treated projectiles. On the other hand, multiple coil inductive sensors and Hall-effect devices can be included on an easily portable muzzle attachment, but do not meet the accuracy requirement because the gradual detection of the projectile by the sensor leads to too much triggering time variability. In addition, they tend to suffer from both zero drift and scale factor differences between the paired sensors.